Cancer patients were studied to evaluate the frequency and significance of pain as a factor in psychological state, functional activity, and course of illness. Frequency of pain in various malignancies varied from 62% in the middle of their clinical course to 95% at the terminal phase. Narcotics were taken in 60-80% of the cases reported pain. Cancer patients with pain appeared to have the same or more total resultant disability but significantly less psychological reactivity. Social support is hypothesized as an attenuating influence on expected effects from pain. Pain patients taking narcotics report more fatigue and mental confusion than those not taking narcotics. A study design is proposed using 450 breast patients in remission and active disease.